The development of transgenic plants having agronomically desirable characteristics often depends on the ability to control the spatial and temporal expression of the polynucleotide responsible for the desired trait. The control of the expression is largely dependent on the availability and use of regulatory control sequences that are responsible for the expression of the operably linked polynucleotide. Where expression in specific tissues or organs is desired, tissue-preferred regulatory elements may be used. Where expression in response to a stimulus is desired, inducible regulatory polynucleotides are the regulatory element of choice. In contrast, where continuous expression is desired throughout the cells of a plant, constitutive regulatory polynucleotides are utilized.
The proper regulatory elements typically must be present and be in the proper location with respect to the polynucleotide in order to obtain expression of the newly inserted transcribable polynucleotide in the plant cell. These regulatory elements may include a promoter region, various cis-elements, regulatory introns, a 5′ non-translated leader sequence and a 3′ transcription termination/polyadenylation sequence.
Since the patterns of expression of transcribable polynucleotides introduced into a plant are controlled using regulatory elements, there is an ongoing interest in the isolation and identification of novel regulatory elements which are capable of controlling expression of such transcribable polynucleotides.